There is currently so much confusion about what to drink, when to drink and how much to drink. My most straightforward advice is to keep it relatively simple.

Always start your day with at least 2 glasses of water (around 16 ounces) shortly after waking up.

Hydrate consistently throughout the day (not just at meals) to ensure that you are not beginning runs in a dehydrated state.

If you are training in extreme heat or humidity OR training or racing over 60 minutes then it is a good idea to take in fluids while running (water or a carbohydrate based drink).

You do not need to drink electrolyte-based drink while training unless you are meeting or exceeding your hydration needs during training or racing (which can lead to a dangerous condition called hyponatremia).